The Langtang valley, running west to east, parallel with the Tibetan border, north of Kathmandu, is a popular trekking area, but nowhere near as crowded as the Khumbu or Annapurna areas. It offers a variety of spectacular scenery from dense forests to austere high mountain landscapes, and spectacular views of the Ganesh, Langtang, and Jugal Himals.
The itinerary below was followed a couple of years ago by two aging (65+) trekkers, as a camping trek, with a full Nepali trekking crew (though for the time in Kyanjin, and at Laurebinayak and Gosainkund lodges were used). From what was seen the lodges were perfectly adequate.
No doubt the itinerary could be shortened by a couple of days if you are younger and fitter